Anti-fouling compositions



United Stats ANTI-FOULING COMPOSITIONS NO Drawing. Application March 10, 1953 Serial No. 341,594

13 Claims. (Cl. 44- 69) This invention relates to compositions which are useful as scavengers with lead anti-knock compounds.

The use of lead compounds in gasolines to increase the octane ratings thereof is extremely widespread. There are, however, several rather serious adverse effects which accompany the use of leaded gasolines. One of these effects, the deposition of various lead compounds within the combustion chambers of the engines, has been at least partially remedied by the use of halohydrocarbon scavengers such as ethylene dibromide. Another adverse effect, which has been attributed to the lead anti-knock compounds, is mis-firing due to spark plug fouling. This spark plug fouling is quite prevalent under conditions of high temperature engine operation and, particularly in the case of aircraft engines, is a very serious type of trouble.

It is, therefore, an object of the present invention to overcome the previous shortcomings arising from the use of leaded gasolines. It is a further object to provide novel scavenger compositions for use with lead anti-knock compounds and in gasoline fuels. Another object is to provide novel fuel compositions containing said scavenger compositions. Other objects will be apparent hereinafter.

It has now been found that the use, as a lead scavenger in stable leaded gasoline fuel compositions, of a mixture of a halohydrocarbon scavenger and of a small amount of an alkaryl phosphate or phosphite containing at least one non-oxygen chalcogen atom, preferably sulfur, in the molecule will result in greater improved operation of spark. ignition internal combustion engines. More particularly, the use of such scavenger compositions substantially eliminates spark plug fouling, or at least minimizes such fouling to a point where it is no longer a material consideration in engine operation. This outstanding advantage is obtained without having the anti-knock characteristics of the fuel deleteriously affected by the pres ence of the scavenger compositions.

The phosphorus compounds in the present scavenger compositions will be referred to hereinafter as anti-fouling compounds.

The halohydrocarbon scavenger which makes up the major proportion of the scavenger compositions of the present invention may be, for example, any of the numerous halogen scavenger compounds already known, such as ethylene dibromide and ethylene dichloride (U. S. 2,398,281), acetylene tetrabromide (U. S. 2,490,606), hexachloropropylene, monoand polyhalo-propanes, butancs and pentanes (U. S. 2,479,900 and U. S. 2,479,902), polyhalo alkyl benzenes (U. S. 2,479,901 and U. S. 2,479,903), and the like, having a volatility between about 100 and about 0.1 mm. Hg at 50 C.

The phosphates and phosphites of the present invention can be readily prepared by reacting phosphorus sulfides, selenides and/ or tellurides with alkyl phenols or with mixtures of alkyl phenols and other types of hydroxy containing organic compounds such as aliphatic, alicyclic and/or heterocyclic alcohols. Another method of preatent 0 paring the phosphorus compounds of this invention is by reacting alkylaryl thiols or salts thereof with phosphorus halides or phosphorus oxyhalides such as P01 or P001 Examples of reactants suitable for forming compounds of this invention include: (a) P 8 P Se P 8 P Se P 'Te PO1 PCl POCl and mixtures thereof and (b) alkyl phenols as well as corresponding derivatives of the sulfur family, e. g., ortho, meta, and para-cresol; 2,4 and 2,5- xylenol; 2,4 dimethyl-6-tert-butyl phenol; octyl and nonyl phenols prepared by alkylation of phenols with diisobutylene or propylene trimer, respectively; diwaxphenol; 2,4 diniethyl selenophenol, diwaxselenophenol; etc.

The trialkaryl thio and/or selenophosphates and phosphites are generally the most suitable anti-fouling agents, but the mono and dialkaryl esters as well as mixed esters containing only one or two alkaryl groups can also be used.

Of the alkaryl radicals the di-, tri-, and higher polyalkylated aromatic radicals are preferred over the monoalkyl aromatic radicals. Higher molecular weight alkyl groups, up to about 12 or 15 carbon atoms, are desirable.

A particularly preferred compound, S,S,.S tri(2,5-dimethylphenyl)-thiophosphate was prepared by first converting 2,5 dimethylphenylthiol to its sodium salt, accomplished by reacting about 2 moles of 2,5 dimethylphenylthiol with 2 moles of 1 N aqueous NaOH solution and thereafter flashing off the water. The dry salt (333 grams) suspended in ether was placed in a flask equipped with a stirrer, C0 -acetone cooled condenser, dropping funnel and thermometer. Through the dropping funnel, 103 grams of P001 was introduced and the mixture reacted for about 8 hours. After the reaction was completed, the ether was flashed off and the mixture washed with 2% aqueous NaOH, followed by water washes and thereafter dried. This solid was filtered and recrystallized in methanol after which the .methanol was removed, leaving behind a white crystalline solid having a melting point of 127 C. and on analysis contained 6.8% P and 21.2% S.

The following are other examples of suitable antifouling additives of the present invention: S,S,S tri- (m-cresyl)thiophosphate; S,S,S tri-(2,4-dimethylphenyl)- thiophosphate; S,S,S tri-(p-ethylphenyl)thionophosphate; 0,0,0 tri (2-methyl-4-isopropylphenyl) thionophosphate; 0,0,0 tri (p-tert-butylphenyl)thionophosphate; 0,0,S tri-(2,6-dimethyl-4-tert-butylphenyl)thiophosphate; S,S,S tri-(4-methyl-1-naphthyl)thiophosphate; O-ethyl S,S di- (p-cresyl)thiophosphate; 2,6-xylenyl S,S-di-t'n-butyl)acid thiophosphate; S,S di-(2-methyl-4-ethy1phenyl)acid thiophosphate; O-mono (o-cresyl)diacid thionophosphate; S,S,S tri[p-(n-propyl)phenyllthiophosphite; S,S,S triEp- (1,1,3,3-tetramethylbutyl) phenyllthiophosphite; S,S,O tri-(2,4,6-trimethylphenyl)thiophosphite; 0,0,5 tri-(p-allylphenyl)thiophosphite; 0,0-di-(tert-amylphenyl acid) thioph-o-sphite; 0, isopropyl S,S-di-(2,5-dimethylphenyl)- thiophosphite; S, S, S (3,5-dimethylphenyl)thiophosphite; S,S-diphenyl O-monop-xenyl thiophosphite; 0,0 di-ochlorophenyl S-mono-o-xenyl thiophosphate; S,S, di-p-tertiarybutylphenyl O-mono-naphthyl thiophosphate; diphenyl mono-p-xenyl thionophosphate; di-p-tolyl-mono-ptertiary octylphenyl thionophosphate; di-o-cyclohexylphenyl mono-2,4-dibromophenyl thionophosphate; dinaphthyl S-mono-p-ethylphenyl thionophosphate; S,S di-oisopropylphenyl O-mono-2,4-dibromphenyl thiophosphate; 0,0-di-m-cyclohexylphenyl S-mono-p-amylphenyl thi ophosphate; di-p-tolyl mono-4-chloro-2 phenyl-phenyl thi0 nophosphate; di-phenyl mono 4 tertiarybutylphenyl-Z- phenyl-phenyl thionophosphate; tricresyl selenonophosphate; trixylenyl selenonophosphate; Se,Se,Se triwaxphenyl selenophosphate; Se,Se,Se triwaxphenyl selenophite; S,S 2-ethylhexyl Se-dicresylphosphate; O-nonyl S,S dicresyl 5 thiophosphate; O-dodecyl S,S-dicresyl thiophosphate; tricresyl thionophosphate; Z-ethylhexyl dicresyl selenonophosphate; tricresyl tellurnophosphate, etc.

The thio, seleno and/or telluro phosphate and/or phosphite compounds of this invention can be supplied to the combustion zone of the engine in various ways to accomplish reduction in fouling of spark plugs due to the combustion of leaded fuels therein. Thus, they can be injected directly into the combustion zone, separately from either or both the fuel and the anti-detonant, or injected directly and separately into the intake manifold, either intermittently or substantially continuously, as desired, or they can be incorporated with the leaded fuel. They can be added separately to the leaded fuel, or they can be blended first with either the gasoline or the anti-detonant; in the latter case, an anti-detonant, scavenger and anti-foulant concentrate is suitably prepared which can be stored and shipped as such and blended with the gasoline as desired.

The following are illustrative examples of compositions suitable for use according to the present invention:

Example I Tetra-ethyl lead 1.0 theory ethylene dibromide 0.2 theories S,S,S tri(2,5,dimethylphenyl)thiophosphate Example IV Tetra-ethyl lead 1.0 theory acetylene tetrabromide 0.4 theory S,S,S tri(p-allylphenyl)thiophosphite Example V 80 octane aviation gasoline containing, per gallon 0.5 cc. tetra-ethyl lead 1.0 theory ethylene dibromide 0.2 theory S,S,S tri(3,5-dimethylphenyl)thiophosphite 0.02 gr. 2,4-dimethyl-6-tertiary-butylphenol Example VI Aviation alkylate containing, per gallon 4.6 cc. tetra-ethyl lead 1.0 theory ethylene dibromide 0.04 gr. 2,4-dimethyl-6-tertiary-butylphenol 0.1 theory O-2-ethylhexyl S,S-dicresyl thiophosphate Example VII Tetra-ethyl lead 1.2 theories hexachloropropylene 0.2 theory 0-2-ethylhexyl 0,0 dicresyl selenonophosphate Example VIII Tetra-ethyl lead 0.8 theory ethylene dibromide 0.2 theory 0,0,0 trixylenyl selenonophosphate Example IX Tetra-ethyl lead 1.5 theories hexachlorobutadiene-1,3 0.1 theory 0,0,0 triwaxphenyl selenonophosphate 4 Example X 76 octane motor fuel containing, per gallon 2.1 cc. tetra-ethyl lead 1.0 theory ethylene dichloride 0.5 theory ethylene dibromide 0.2 theory 0,0,0 triwaxphenyl selenonophosphite Example XI /145 grade aviation gasoline containing, per gallon 4.6 cc. tetra-ethyl-lead 1.0 theory ethylene dibromide 0.2 theory S,S,S tri(2,5 dirnethylphenyl)thiophosphate Example XII Tetra-ethyl lead 0.5 theory ethylene dibromide 0.1 theory 0,0 dicyclohexylphenyl thiophosphate Example XIII Tetra-ethyl lead 0.8 theory ethylene dichloride 0.2 theory tricresyl selenonophosphate Example XIV Tetra-ethyl lead 1.0 theory ethylene dibromide 0.1 theory S,S,S tri(p-allylphenyl)thiophosphate Example XV Motor gasoline, containing, per gallon 1.6 cc. tetra-ethyl lead 1.0 theory hexachlorethane 0.2 theory S,S,S tri(2,5 dimethylphenyl)thiophosphate 0.06 gr. N-butyl-p-aminophenol Example XVI Tetra-ethyl lead 1.0 theory ethylene dibromide 0.06 theory S,S,S tri[p-(n-propyl)phenyl]thiophosphate Example XVII Tetra-ethyl lead 1.0 theory ethylene dibromide 0.5 theory S,S,S tri(2,6 dimethyl 4 tert butylphenyl) thiophosphate Example XVIII Tetra-ethyl lead 0.8 theory ethylene dibromide 0.2 theory S mono(o-cresyl)diacid thiophosphate As already indicated, the order of mixing the various constituents of the present compositions is immaterial. For example, the anti-fouling compound may be added to a gasoline which already contains the anti-knock compound and halogen scavenger. Likewise, the metalloorganic anti-knock agent, the halogen-scavenger and the anti-fouling compound may be first mixed, stored and handled as a concentrate, and added to the gasoline at a later time. A typical concentrate of this latter type has approximately the following composition:

Weight percent Tetra-ethyl lead 55-60 Ethylene dibromide 25-30 S,S,S tri(2,5-dimethylphenyl)thiophosphate 10-15 Kerosene, inhibitor, dye stabilizer, etc 36 Under other circumstances it may be desirable to mix the halogen scavenger and the anti-fouling agents, or

detonant present.

it? the anti-knock agent and the anti-fouling agent, in the desired relative proportions and handle or store this mixture, with or without stabil zers, inhibitors, etc., as a concentrate for later incorporation with the other components of the ultimate fuel composition.

When using the scavenger compositions of the present invention, the total amount of halogen scavenger plus anti-fouling agent will generally fall between about 0.6 and about 1.5 theories, based upon the lead content of the gasoline, but may advantageously be as low as 0.4 or as high as 2.0 in some cases. The preferred range is from about 0.9 to about 1.2 theories.

The ratio of the two components of the scavenger composition is rather important. For example, if the proportion of halogen scavenger present is too large, excessive wear and corrosion of certain operating parts, such as exhaust valves and valve guides is noted. If too small a quantity of halogen scavenger is used, the lead deposits are not effectively scavenged. If too small a quantity of the anti-fouling compound is used, the spark plug fouling will not be materially reduced; and if too much of that compound is present the amounts of deposits and the plug fouling both may be increased. In general, the theory ratio of the halogen scavenger or scavengers to the antifouling agents should be between about 3:2 and about 100:1. For best results this ratio should be between about 2:1 and about 15:1. As an additional limitation, the total scavenger mixture and the ratio of components therein should be adjusted so that the anti-fouling compound is present in an amount of between about 0.01 and about 0.6 theories, and preferably between about 0.1 and about 0.2 or if desired between about 0.05 and about 0.4 theories. A particularly desirable composition comprises 1 theory of the halogen scavenger and 0.1 theory of the anti-fouling compound. It is to be understood that more than one of the compounds from each class (i. e., halogen scavenger or anti-fouling agent), may be used in any single composition, just so the total quantity of each type falls within the limits set forth above.

The term theory, when used in conjunction with a halogen scavenger compound, designates the amount of scavenger required to react stoichiometrically with agiven amount of lead anti-detonant so that all of the lead atoms :and all of the halogen atoms form PbB-r or PbCl In other words, a theory of scavenger is an amount which contains two atomic proportions halogen for each atomic proportion of lead in the anti-detonant, or, a theory of the halohydrocarbon scavenger is one mol of the halohydrocarbon scavenger divided by one-half the number of halogen atoms per molecule, for each gram atom of lead in the lead anti-detonant present, and therefore, the number of theories of halohydrocarbon scavenger present in a given composition is equal to the number of mols of halohydrocarbon scavenger present multiplied by one-half the number of halogen atoms per molecule, for each gram atom of lead in the lead anti- As applied to phosphorus containing anti-fouling compounds, the term theory designates the amount required to react stoichiometrically with the lead so that all of the lead atoms and all of the phosphorus atoms could be in the form of Pb (PO that is, two atomic proportions of phosphorus for each 3 atomic proportions of lead. Therefore, a theory of the phosphorus anti-fouling compound is one mol of the phosphorus anti-fouling compound multiplied by twothirds (that is, two-thirds of a mol of the phosphorus anti-fouling compound), for each gram atom of lead in the lead anti-dctonant present, and therefore the numer of theories of phosphorus anti-fouling compound present in a given composition is equal to the number of mols of the phosphorus anti-fouling compound present multiplied by three-halves, for each gram atom of lead in the lead anti-detonantpresent.

6 While it is to be understood that the present compositions may be utilized in any leaded gasoline fuel, the compositions are of particular importance with respect to use in reciprocating internal combustion engine gasoline fuels, and especially such aviation fuels. This is true because of the relatively more frequent occurrence of spark plug fouling in spark ignition aviation engines,

with the greater inherent danger to human life in the case of failures of such engines. In addition to the lead anti-detonant and the scavenger compositions, the gasoline fuels, or the concentrates for addition thereto may also contain corrosion inhibitors and stabilizers, such as 2,4-dimethyl-6-tertiary-butylphenol and other alkyl phenols, N,N-dibutyl-p-phenylene diamine, hydroquinone, phenyl alpha naphthylamine, N-butyl-p-aminophenol, alphauiaphthol, etc., dyes and the like.

By the term leaded gasoline, and the terms of similar import, is meant a petroleum fraction boiling in the gasoline hydrocarbon range (between about. 50 F. and about 450 F.) to which has been added a small amount, usually between about 1 and about 6 cc. per gallon, of a metallo-organic, usually an organo-lead, anti-knock compound, such as a tetra-alkyl lead, e. g., tetra-ethyl lead, tetra-i-propyl lead, etc.

The fuels to which the present scavenger compositions are added are preferably those which are relatively stable with respect to oxidation or gum formation. The stability may result from the use of stable base stocks such as aviation alkylate, straight run gasoline fractions, or other fractions which have been highly refined to remove olefins, or the stability may result from the use of oxidation stabilizers, such as those mentioned above. The term stable gasoline as used herein refers to gasoline fuels having a maximum of 5 mg. existent gum per ml. of fuel (ASTM D-381-50), and a maximum of 10 mg. of gum per 100 ml. of gasoline after accelerated aging for 16 hours at 100 C. and 100 p. s. i. 0 pressure. (The foregoing gum values apply to the fuel before addition of non-volatile additives, such as the anti-fouling agents of the present invention.)

As indicated above, the scavenger compositions of this invention are particularly useful in aviation gasolines. By the term aviation gasoline is meant a relatively high frade of gasoline fuel used in aviation engines, as distinguished from the lower quality gasolines, or motor fuels used inautomotive engines. Aviation fuels have a more clearly specified boiling range, generally running from a minimum of about 100 F. to a maximum of about 350 F. The anti-knock rating of such fuels is often appreciably higher than that of 100 octane number gasoline. Because of the demand for high quality, thermally cracked fractions are never used in aviation gasolines. Catalytically cracked fractions may sometimes be used, but only after treatment to remove olefins. One of the reasons for the restrictions upon incorporation of cracked gasolines in aviation fuels is that the oxidation stability of aviation fuels must be much greater than that required for motor fuels. For example, when tested according to a method such as described in the patent issued to Thomas W. Bartram, U. S. 2,256,187, an aviation fuel base stock will go well beyond 4- or 5 hours before the oxygen pressure will have decreased by 5 pounds per square inch.

The present application is a continuation-in-part of our copending application Serial No. 242,309, filed August 17, 1951, and now abandoned which is in turn'a continuation of our application Serial No. 167,376, filed June 10, 1950, now abandoned.

We claim as our invention:

1. A fuel composition for internal combustion engines consisting essentially of a stable gasoline, a minor effective anti-detonant amount of a tetra lower alkyl lead antidetonant, and a scavenger mixture for said anti-detonant consisting essentially of a halohydrocarbon scavenger and a phosphorus tri-ester compound selected from the group consisting essentially of alkaryl thiomonophosphates and alkaryl thiomonophosphites, said halohydrocarbon scavenger and said phosphorus compound being present in amounts such that, where (a) is the number of mols of said halohydrocarbon scavenger present multiplied by one-half the number of halogen atoms per molecule for each gram atom of lead in the lead anti-detonant present, and (b) is the number of mols of said phosphorus compound present multiplied by three-halves, for each gram atom of lead in the lead anti-detonant present, the total of (a) plus (b) is from about 0.4 to about 2.0, (b) is from about 0.01 to about 0.6, and the ratio of (a) to (b) is from about 3:2 to about 100:1.

2. A gasoline fuel additive composition consisting essentially of a tetra lower alkyl lead anti-detonant and a scavenger mixture for said anti-detonant consisting essentially of a halohydrocarbon scavenger and of a phosphorus tri-ester compound selected from the group consisting of alkaryl thiomonophosphates and alkaryl thiomonophosphites, said halohydrocarbon scavenger and said phosphorus compound being present in amounts such that where (a) is the number of mols of said halohydrocarbon scavenger present multiplied by one-half the num ber of halogen atoms per molecule, for each gram atom of lead in the lead anti-detonant present, and (b) is the number of mols of said phosphorus compound present multiplied by three-halvesffor each gram atom of lead in the lead anti-detonant present, the total of (a) plus (b) is from about 0.4 to about 2.0, (b) is from about 0.01 to about 0.6, and the ratio of (a) to (b) is from about 3:2 to about 100:1.

3. A lead scavenging composition for use With a gasoline fuel for internal combustion engines which gasoline fuel contains -a tetra-lower-alkyl-lead anti-detonant, consisting essentially of a halohydrocarbon scavenger and of a phosphorus tri-ester compound selected from the group consisting of alkaryl thiomonophosphates and alkaryl thiomonophosphites, s'aid halohydrocarbon scavenger and said phosphorus compound being present in amounts such that where (a) is the number of mols of said halohydrocarbon scavenger present multiplied by one-half the number of halogen atoms per molecule, and (b) is the number of mols of said phosphorus compound present multiplied by three-halves, the ratio of (a) to (b) is from about 3:2 to about 100: 1.

4. A composition in accordance with claim 1, wherein the phosphorus compound is an alkaryl thiomonophosphate.

5. A composition in accordance with claim 1, wherein the phosphorus compound is an alkaryl thiomonophosphite.

6. A composition in accordance with claim 1, wherein the phosphorus compound is tricresyl thionophosphate.

7. A composition in accordance with claim 1, wherein the phosphorus compound is S,S,S-tricresyl thiophosphate.

8. A composition in accordance with claim 1, wherein the phosphorus compound is S,S,S-tri(2,5-dimethylphenyl)-thiophosphate and wherein the gasoline is an aviation gasoline boiling within the range between about 100 F. and 350 F., having an octane number higher than 100 and containing no thermally cracked gasoline fractions and no olefinic cat-alytically cracked gasoline fractions.

9. A fuel composition for internal combustion engines consisting essentially of a stabilized automotive gasoline,

a minor elfective anti-detonant amount of tetraethyl lead, and a scavenger mixture for said tetraethyl lead consisting essentially of ethylene dibromide, ethylene dichloride, and a phosphorus tri-ester compound selected from the group consisting of alkaryl thiomonophosphates and alkaryl thiomonophosphites, said ethylene dibromide, ethylene dichloride and phosphorus compound being present in amounts such that where (a) is the total number of mols of said ethylene dibromide and ethylene dichloride present, for each mol of tetraethyl lead present and (b) is the number of mols of said phosphorus compound present multiplied by threehalves, for each mol of tetraethyl lead present, the total of (a) plus (b) is from about 0.4 to about 2.0, (b) is from about 0.01 to about 0. 6, and the ratio of (a) to (b) is from about 3 :2 to about :1.

10. A fuel composition for internal combustion engines consisting essentially of a stable gasoline, a minor effective anti-detonant amount of tetraethyl lead, and a scavenger mixture for said tetraethyl lead consisting essen-tially of a halohydrocarbon scavenger and a phosphorus tri-ester compound selected from the group consisting of alkaryl thiomonophosphates and alkaryl thiomonophosphites, said halohydrocarbon scavenger and said phosphorus compound being present in amounts such that, where (a) is the number of mols of halohydrocarbon scavenger present multiplied by one-half the number of halogen atom-s per molecule, for each mol of tetraethyl lead present, and (b) is the number of mols of said phosphorus compound present multiplied by three-halves, for each mol of tetraethyl lead present, the total of (a) plus (b) is from about 0.4 to about 2.0, (b) is from about 0.05 to about 0.4 and the ratio of (a) to (b) is at least 3:2.

11. A fuel composition for internal combustion engines consisting essentially of a stabilized automotive gasoline, a minor effective anti-detonant amount of tetraethyl lead, and a scavenger mixture for said tetraethyl lead consisting essentially of ethylene dibromide, ethylene dichloride and S,S,S tri(2,5-dimethylphenyl)thiophosphate, said ethylene dibromide and ethylene dichloride being present in amounts such that the total number of mols of ethylene dibromide and ethylene dichloride, for each mol of tetraethyl lead present, is about 1.5, and said S,S,S-tri(2,5-dimetl1ylphenyl)thiophosphate being present in amounts such that the number of mols of said S,S,S- tr-i(2,5-dimethylphenyl) thiophosphate multiplied by threehalves, for each mol of tetraethyl lead present, is about 0.2.

12. A fuel composition for internal combustion engines consisting essentially of a stable aviation gasoline, a minor effective anti-de-tonant amount of tetraethyl lead, and a scavenger mixture for said tetraethyl lead consisting essentially of ethylene dibromide and S,S,S-tricresyl thiophosphate, said ethylene dibromide being present in an amount such that the number of mols of ethylene dibromide, for each mol of tetraethyl lead present, is about 1.0, and said S,S,S-tricresyl thiophosphate being present in an amount such that the number of mols of said S,S,S-tricresyl thiophosphate multiplied by three-halves, for each mol of tetraethyl lead present, is about 0.1.

13. A fuel composition for internal combustion engines consisting essentially of a stable aviation gasoline boiling within the range between about 100 F. and 350 F., having an octane number higher than 100 and containing no thermally cracked gasoline fractions and no olefinic catalytically cracked gasoline fractions, from about 1 to about 6 ccs. of tetraethyl lead per gallon of fuel, and a scavenger mixture for said tetraethyl lead consisting essentially of ethylene dibromide and S,S,S-tri(2,5-dimethylphenyDthiophosphate, said ethylene dibromide being present in an amount such that the number of mols of ethylene dibromide, for each mol of tetraethyl lead present is about 1.0, and said S,S,'S-tri(2,5-dimethylphenyl) thiophosphate being present in an amount such that the number of mols of said S,S,S-tri(2,-5-dimethylphenyl) thiophosphate multiplied by three-halves, for each mol of tetraethyl lead present, is about 0.1.

References Cited in the file of this patent UNITED STATES PATENTS 2,245,649 Caprio June 17, 1941 2,405,560 Campbell Aug. 13, 1946 2,599,341 McDermott June 3, 1952 FOREIGN PATENTS 600,191 Great Britain Apr. 2, 1948 500,535 Belgium Jan. 31, 1951 

1. A FUEL COMPOSITION FOR INTERNAL COMBUSTION ENGINES CONSISTING ESSENTIALLY OF A STABLE GASOLINE, A MINOR EFFECTIVE ANTI-DETONANT AMOUNT OF A TETRA LOWER ALKYL LEAD ANTIDETONANT, AND A SCAVENGER MIXTURE FOR SAID ANTI-DETONANT CONSISTING ESSENTIALLY OF A HALOHYDROCARBON SCAVENGER AND A PHOSPHORUS TRI-ESTER COMPOUND SELECTED FROM THE GROUP CONSISTING ESSENTIALLY OF ALKARYL THIOMONOPHOSPHATES AND ALKARYL THIOMONOPHOSPHITES, SAID HALOHYDROCARBON SCAVENGER AND SAID PHOSPHORUS COMPOUND BEING PRESENT IN AMOUNT SUCH THAT, WHERE (A) IS THE NUMBER OF MOLS OF SAID HALOHYDROCARBON SCAVENGER PRESENT MULTIPLIED BY ONE-HALF THE NUMBER OF HALOGEN ATOMS PER MOLECULE FOR EACH GRAM ATOM OF LEAD IN THE LEAD ANTI-DETONANT PRESENT, AND (B) IS THE NUMBER OF MOLS OF SAID PHOSPHORUS COMPOUND PRESENT MULTIPLIED BY THREE-HALVES, FOR EACH GRAM ATOM OF LEAD IN THE LEAD ANTI-DETONANT PRESENT, THE TOTAL OF (A) PLUS (B) IS FROM ABOUT 0.4 TO ABOUT 2.0, (B) IS FROM ABOUT 0.01 TO ABOUT 0.6, AND THE RATIO OF (A) TO (B) IS FROM ABOUT 3:2 TO ABOUT 100:1. 